The energies and entropies of activation for reaction of opsin with a series of retinal analogues modified in the 9-position will be determined. CD spectra of a number of visual pigment analogues will be studied. 10,13-CH2, 11-cis retinal; 5,6-dihydroretinal; 11,12- dihydroretinal; and 5-vitaldehyde will be synthesized and their reactions with opsin studied. Vis-UV and CD spectra of visual pigment analogues will be studied. A theoretical basis for the spectral properties of retinal analogues and analog pigments will be obtained. N- bromosuccinimide (NBS) and N-acetylimidazole (NAI) will be used to modify the properties of tryptophan and tyrosine residues on opsin. Complexes of retinal and its analogs with tyrosine and tryptophan will be prepared. The rates of reaction of frog and chicken opsin with retinal and its analogs will be studied.